1. Field of the Invention
The present invention relates to a blur correction apparatus employed in conjunction with a lens barrel of a silver halide camera, a so-called digital still camera or the like, which corrects an image blur by moving part of or the entirety of the photographic lens.
2. Description of the Related Art
Concentrated efforts have been made in recent years to establish technologies for correcting a blur of an image photographed with a camera by detecting camera vibration and partially moving the lens along the direction of the camera vibration so as to correct the image blurring on the film surface. We have also seen a significant advance of so-called digital still cameras (hereafter referred to as DSCs) that utilize photoelectric conversion elements as image-capturing elements without using any film in recent years. A DSC normally includes a liquid crystal viewfinder and a liquid crystal monitor. Since it requires a considerable amount of power for arithmetic processing and the like executed on images as well, it consumes a great deal of power. Accordingly, reducing the power requirement in the DSC is important.
In addition, the DSC, having an image-capturing surface smaller in size compared to the silver halide format size in the related art and thus having a smaller image circle in the optical system, makes it possible to reduce the size of the components of the lens barrel. Accordingly, high expectations are placed on the DSC for its potential for achieving miniaturization.
At the same time, as an increasingly higher magnification factor is assured and also the magnification factor can be raised freely through image processing (the so-called digital zoom), it is preferable for the DSC to have an accurate blur correction function. For instance, the magnification may be raised by a factor of 8 through optical zoom and then it may be further raised through digital zoom. In such a case, the likelihood of hand movement causing image blurring in long focal point photographing becomes higher. Thus, it is essential that cameras having long focal point capability be equipped with a blur correction function. For this reason, the DSC today comes equipped with a blur correction apparatus.
The blur correction unit used in conjunction with a blur correcting interchangeable lens requires a lock mechanism that mechanically holds the blur correcting lens at a predetermined position in the related art, since the blur correcting interchangeable lens may be mounted at a camera which is not capable of supplying power and the position of the blur correcting lens becomes indeterminate in such a case. The lock mechanism is also necessary in a camera compatible with the blur correcting interchangeable lens, in order to prevent the position of the blur correcting lens from becoming indeterminate when the blur correction function is not engaged.
However, the presence of the blur correcting lens lock mechanism presents difficulties in miniaturizing the components of the lens barrel, leading to a problem of an increase in the camera size. The presence of the lock mechanism places a particularly significant hindrance to achieving miniaturization of a DSC which does not allow lens exchange.
Now, let us examine a structure that does not include the blur correcting lens lock mechanism. In a blur correction-enabled state in which a blur correction operation is enabled (in a blur correction ON state), the blur correcting lens is driven and thus, the position of the blur correcting lens does not become indeterminate. However, in a blur correction-disabled state in which the blur correction operation is not enabled (in a blur correction OFF state), the position of the blur correcting lens will become indeterminate without a lock mechanism and thus the problem arises in that the desired optical performance cannot be achieved during the photographing operation. In addition, there is another problem in that if the camera includes a flash device having a light emission unit which pops up, for instance, the blur correcting lens is bound to move when the light emission unit is deployed, resulting in a movement of the image displayed at the liquid crystal viewfinder, the liquid crystal monitor and the like.
These problems may conceivably be eliminated through a method in which control is implemented to hold the blur correcting lens at a constant position at all times by, for instance, constantly supplying power to a VCM to prevent any movement of the blur correcting lens.
However, since power must be constantly supplied to the VCM in order to hold the blur correcting lens at the set position at all times, a great deal of power is required, which leads to a reduction in the battery service life. Thus, in view of the need to minimize power consumption in the DSC explained earlier, it is difficult to assure enough power to control the blur correcting lens so as to hold it at the set position at all times.